Fuze internal oscillator calibration system, method, and apparatus

ABSTRACT

A system, apparatus, and method for detonating a projectile which includes receiving data by a microprocessor located in the projectile from an external ballistic computer. Calibrating a low frequency oscillator located in the projectile using an internal precision reference oscillator also located in the projectile that can withstand launch accelerations of tens of thousands of g&#39;s. Powering off the reference oscillator when calibration is complete to save energy and transmitting a detonation signal from the microprocessor to a detonation circuit located in the projectile.

RELATED ART

This application is related to U.S. Pat. No. 5,942,714, to Richard Oberlin and Robert Soranno, titled Accurate Ultra Low Power Fuze Electronics, assigned to the AAI Corporation, Hunt Valley Md., the contents of U.S. Pat. No. 5,942,714 are hereby incorporated herein in their entirety by reference.

BACKGROUND Field of the Invention

The present invention relates generally to a new and improved fuze design to simplify the interface between the fuze electronics and the fire control system.

SUMMARY

In an embodiment of the present invention, a self contained fuze apparatus is disclosed. This embodiment includes a power supply, a power conditioner electrically connected to the power supply, a microprocessor connected to the power conditioner, an oscillator connected to the microprocessor, a reference oscillator connected to the microprocessor, and a detonation circuit connected to the microprocessor and the power conditioner. In this embodiment, the reference oscillator directly calibrates the oscillator.

In another embodiment of the present invention, a projectile detonation system is disclosed. This embodiment includes a ballistic computer, a projectile, and a microcontroller located on the projectile. In this embodiment, the microcontroller includes a microprocessor, a low frequency oscillator, a reference oscillator, and a detonation circuit. In this embodiment, the Microprocessor is capable of receiving detonation timing data from the ballistic computer and is connected to the low frequency oscillator and the detonation circuit. In this embodiment, the reference oscillator is capable of calibrating the low frequency oscillator.

In yet another embodiment of the present invention, a method includes: receiving data by an internal microprocessor from an external ballistic computer, where the microprocessor is located in said projectile and the ballistic computer is located external to the projectile in a Fire Control System (FCS); calibrating an internal low frequency oscillator coupled to the microprocessor via an internal reference oscillator located in the projectile, where the low frequency oscillator can withstand launch accelerations of tens of thousands of g's; powering off the reference oscillator on completion of calibration; and transmitting from the microprocessor a detonation signal to a detonation circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustrative block diagram of a fuze internal oscillator calibration system with an exemplary power switch;

FIG. 2 depicts an illustrative block diagram of a fuze internal oscillator calibration system with an exemplary enable function;

FIG. 3 depicts an illustrative block diagram of a fuze internal oscillator calibration device powered by the microprocessor;

FIG. 4 depicts an illustrative block diagram of a known fuze external oscillator calibration device; and

FIG. 5 depicts an illustrative block diagram of a fuze internal oscillator calibration system.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

An illustrative embodiment of the invention is discussed in detail below. While specific illustrative embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention.

An illustrative embodiment of the invention relates generally to a new and improved fuze design used to detonate munitions. The fuze circuit may be disposed in a projectile that requires accurate detonation timing. In one embodiment, an internal fuze (i.e., internal to the projectile) may be used in, for example, 50 caliber and larger (e.g., but not limited to, up to 155 mm) projectiles. External to the projectile, a Fire Control System (FCS) may be used to determine the desired range for the fuze to optimally detonate the projectile. Once the desired range is determined, the time to detonation from launch may be calculated. The required data may be transferred from the external FCS to the internal fuze of the projectile. The data can be of a variety of types depending on the weapon it is installed in. The data type can be, for example, Mode, Target Range, Event Time, diagnostics, or Ballistic Data.

The internal fuze may utilize an internal microprocessor which may process data and, based on the data, detonate the accompanying projectile at the appropriate time and distance from launch.

FIG. 4. depicts a block diagram of a known fuze external oscillator calibration device. Data 430 processed by the ballistic computer 435 is transferred to a required modulator 425. Output from an external precision high frequency oscillator 445 is also sent to the modulator 425. Data then travels over the data link 420 to the microprocessor 410 to calibrate a high frequency oscillator 405. The microprocessor 410 of the fuze electronics 485 is preprogrammed with the precise frequency of the external FCS oscillator 445.

Thus, any oscillators internal to the fuze and projectile must be calibrated from a source external to the fuze and projectile and are therefore, not directly calibrated. As a result of the need to convey or preprogram the exact frequency from the FCS 445 to the microprocessor 410, there is a one-to-one relationship between the fuze electronics 485 and the FCS 450. In other words, a particular internal fuze electronics 485 only works with a particular FCS 450.

An illustrative embodiment of the internal oscillator calibration of the current invention may eliminate the dependence on having to convey or preprogram the precise frequency of the external FCS oscillator parameters into the internal fuze.

FIG. 1 depicts an illustrative block diagram of a fuze internal oscillator calibration system with an exemplary power switch 155.

In an exemplary embodiment, DC power from power source 105, is initially routed to power conditioner and storage component 160. The DC power source 105 may be attained, for example, via a piezo power source, a battery, an external circuit, or other means to supply electric current. The DC power source 105 may vary in current and voltage and the power conditioner and storage component 160 may be used to supply a constant and steady source of power even after the power source 105 stops supplying power. For example, the power conditioner and storage component 160 may store and condition a charge from the power source 105 (e.g., but not limited to a piezoid power source) at the time of projectile launch and acceleration. Alternatively, power may be obtained when a projectile containing the fuze is initially placed in a weapon breech or gun barrel (not shown). The particular storage capacitor 160 used, is a function of the DC Power Voltage (Vcc) being supplied, how long the projectile has to operate, and the volume available.

Conditioned power may be supplied to the microprocessor 110, the power switch 155, and the detonator 145. In one embodiment, the microprocessor 110, via a control port 130, may enable and/or disable power to the precision reference oscillator 115 through the use of the power switch 155.

In one embodiment of the current invention, a sacrificial reference oscillator such as the precision reference oscillator 115 is used for calibration. The sacrificial reference oscillator may be considered internal as it is part of the fuze and may be launched with the projectile. The precision reference oscillator 115 may calibrate either the high frequency oscillator 120 or the low frequency oscillator 125, the oscillators 120, 125 may, for example, be of a resistor-capacitor (RC) type oscillator. The oscillators 120, 125 may be of any type, for example, that can survive the high launch g's, be stable for a matter of several seconds and draw low power. Thus, the microprocessor 110 and/or oscillators 125, 120 may be directly calibrated (i.e., calibrated internally to the fuze) via the precision reference oscillator 115. Precision reference oscillator 115 could be the only oscillator required if it could meet the criteria listed above, but such an oscillator has not yet been developed.

The precision reference oscillator 115 may only be powered on for a short time (e.g., but not limited to, 1 to 200 milliseconds), if the precision reference oscillator 115 current draw exceeds the available power (e.g., when the precision reference oscillator 115 operates at a high frequency). A sufficiently accurate, for example, +/−0.05% or better, oscillator may be required for proper calibration. In one embodiment, the precision reference oscillator 115 may not need to survive a high g-force environment since the calibration may take place prior to projectile acceleration and a common crystal oscillator may be sufficient for the precision reference oscillator 115.

However, in another embodiment, the precision reference oscillator 115 may be required to survive in a high g-force environment. Although commonly used crystal oscillators may have sufficient accuracy, it may be impractical for a crystal oscillator to be used as the precision reference oscillator 115. Crystal oscillators may not survive launch accelerations of tens of thousands of g's. High speed projectiles, especially those with a piezo power source 105, may require the precision reference oscillator 115 to remain operational during accelerations of tens of thousands of g's. With a piezo powered projectile, there may be no voltage available until the projectile begins accelerating. Further, the precision reference oscillator 115 may require operation within milliseconds (e.g., but not limited to, 1 to 200 milliseconds) so that the microprocessor 110 can be programmed early in the firing cycle. Small size and weight may also be important for the precision reference oscillator 115 because of limitations imposed by the size of the projectile and the attendant fuze cavity.

A table illustrating an exemplary Event vs. Time is shown below:

Event Time (1) Projectile placed in Breech Dependent on the Scenario (2) Target Acquired Dependent on the Scenario (3) Target Data sent to FCS When Target is Acquired (4) FCS calculates Time to Detonate Continuously (5) Power applied to Fuze During 0 to 20 ms (6) Lo Frequency Oscillator Calibration During power-up (7) Hi Frequency Oscillator turned Off 20 ms point (8) Data sent from FCS to Fuze During 20 to 35 ms (9) Data Verification back to FCS During 35 to 50 ms (10) Trigger Pulled Time 50 ms (11) Projectile Fired 50 ms (12) Microproc. sends signal to Detonator From 50 ms to seconds (13) Projectile high explosive (HE) explodes

Recently available silicon reference oscillators can survive tens of thousands of g's and the calibration may be concluded before the oscillator fails, mechanically, even if levels above tens of thousands of g's are reached. Several exemplary silicon oscillators that may be used include the CWX813-16.0M oscillator manufactured by Connor Winfield Corp., the FXO-HC735-16MHz oscillator manufactured by Fox Electronics, the KC2520B25.0000C2GE00 oscillator manufactured by AVX Corp., DSC1030 oscillator manufactured by Discera, Inc., the C3392-16.0000 oscillator manufactured by Crystek Corp., and the EMK22H2H-20.000M oscillator manufactured by Ecliptek Corp.

Calibration information from the precision reference oscillator 115 may travel from the precision reference oscillator 115 via an output port 140 to an input port 135 on the microprocessor 110. In one embodiment, the precision reference oscillator 115 calibrates the high frequency oscillator 120, the high frequency oscillator 120 may then calibrate the low frequency oscillator 125. In another embodiment, the precision reference oscillator 115 directly calibrates the low frequency oscillator 125. In another embodiment, the high frequency oscillator 120 and the low frequency oscillator 125 may be one element.

For precise fuze detonation, the low frequency oscillator 125 may require accurate calibration to +/−0.1% or better. The low frequency oscillator 125 typically operates at a low enough frequency to enable the circuit to draw low enough current so that it may operate from the power stored in the power conditioner and storage component 160 even after no power is supplied from DC power source 105. On the other hand, the high frequency oscillator 120 may operate at a frequency in the MHz region.

The microprocessor, 110 may calculate the appropriate time to detonate, at which point, the microprocessor 110 may send a detonation command from, for example, port 3 150 to the detonation circuit 145.

FIG. 2 depicts an illustrative block diagram of a fuze internal oscillator calibration system with an exemplary enable function. In one embodiment, the precision reference oscillator 215 includes an “enable” function which may allow the microprocessor 210 to enable the precision reference oscillator 215 either before the launch of the accompanying projectile or just after the projectile begins accelerating. For example, port 1 230 of the microprocessor 210 may be used to send an enable signal to the precision reference oscillator 215 port 205. The power source 105 may supply power to the power conditioner and storage component 160. Power from the power conditioner and storage component 160 is not drawn by the precision reference oscillator 215, for example, until the precision reference oscillator 215 is enabled by the microprocessor 210.

FIG. 3 depicts an illustrative block diagram of a fuze internal oscillator calibration device directly powered by the microprocessor. In one embodiment, if the precision reference oscillator 315 current requirement is low enough, the microprocessor 310, via microprocessor port 330, may supply the power to the precision reference oscillator 315, via oscillator connection 305. In one embodiment, the microprocessor 310 may use the precision reference oscillator 310 for calibration. In another embodiment, the precision reference oscillator 315 may calibrate an oscillator 325 which may be electrically coupled to the microprocessor 310. The oscillator 325 may operate at a single frequency between, for example, somewhere in the range of, for example, 1 KHz to 20 KHz.

FIG. 5 depicts an illustrative block diagram of a fuze internal oscillator calibration system. Once the projectile 590 is loaded into the breech of a weapon or weapons system (not shown) or gun barrel (not shown), data 530 may be received by the ballistic computer 535 in the FCS 550. Data 540 is then transmitted from the ballistic computer 535 to microprocessor 510 without the need for conveying or preprogramming precise oscillator values from the FCS 550 to the fuze electronics 585. The microprocessor 510 is part of the fuze electronics 585 which is part of the projectile 590. The power supplied by power source 105 may be from a piezoid, a battery, an external circuit, or any other known power source. Power source 105 supplies power to the power conditioner and storage component 160. With steady power supplied by the power conditioner and storage component 160, the precision oscillator 515 may calibrate oscillator 520. The oscillator 520 may independently operate within, for example, the below the 100 kHz range. Oscillator 520 may be in the same or different circuit as microprocessor 510.

When the appropriate length of time has expired, microprocessor 510 issues a detonation signal to the detonation circuit 145. The detonation circuit 145 detonates explosive 560 causing the projectile 590 to explode. Various actions can take place such as a warhead exploding, release of a payload, etc. HE is normally activated because its action is rapid. The projectile may also have a default mechanism (not shown) for triggering detonator 145 in the event of a malfunction within the fuze electronics 585.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. The sizes and ranges may change depending on the various embodiments of the invention. For example, the rate of oscillation of the reference oscillator 115 may change depending on the weapon and type of projectile used (e.g., the fuze electronics used for a 50 caliber round may be different from a 155 mm round). Thus, the breadth and scope of the present invention should not be limited by any of the above-described illustrative embodiments, but should instead be defined only in accordance with the following claims and their equivalents 

1. A self contained fuze apparatus comprising: a power supply; a power conditioner electrically coupled to said power supply; a microprocessor coupled to said power conditioner; a first oscillator coupled to said microprocessor; a reference oscillator coupled to said microprocessor, wherein said reference oscillator is operable to directly calibrate said first oscillator; and a detonation circuit coupled to said microprocessor, said detonation circuit coupled to said power conditioner.
 2. The fuze apparatus of claim 1, further comprising a microcontroller located in a projectile, wherein said microcontroller comprises: said power conditioner; said microprocessor; said first oscillator; said reference oscillator; and said detonation circuit.
 3. The fuze apparatus of claim 1, wherein said reference oscillator is capable of operating within 1 to 200 milliseconds of receiving power.
 4. The fuze apparatus of claim 1, wherein said reference oscillator is capable of withstanding launch accelerations of tens of thousands of g's.
 5. The fuze apparatus of claim 1, wherein said reference oscillator comprises a low frequency oscillator.
 6. The fuze apparatus of claim 1, further comprising: a low frequency oscillator coupled to said microprocessor, wherein said reference oscillator is a high frequency oscillator coupled to said microprocessor.
 7. The fuze apparatus of claim 1, wherein said reference oscillator includes an enable function operable by said microprocessor.
 8. The fuze apparatus of claim 1, further comprising: a power switch electrically coupled to said reference oscillator, wherein said power switch is operable by said microprocessor.
 9. The fuze apparatus of claim 6, wherein said low frequency oscillator oscillates at a frequency less than or equal to 100 KHz.
 10. The fuze apparatus of claim 6, wherein said high frequency oscillator oscillates at a frequency greater than 100 KHz.
 11. The fuze apparatus of claim 6, wherein said low frequency oscillator and said first oscillator are resistor-capacitor (RC) oscillators.
 12. The fuze apparatus of claim 1, wherein said reference oscillator comprises an all silicon resonator.
 13. The fuze apparatus of claim 1, wherein said power supply comprises a piezoid power source.
 14. The fuze apparatus of claim 1, wherein said power supply comprises a battery power source.
 15. The fuze apparatus of claim 1, wherein said power supply comprises a external circuit.
 16. The fuze apparatus of claim 1, wherein said reference oscillator is operable on a separate circuit from said microprocessor.
 17. A system of detonating a projectile comprising: a ballistic computer; a microcontroller located on said projectile, said microcontroller comprising: a microprocessor operable to receive detonation timing data from said ballistic computer; a low frequency oscillator coupled to said microprocessor; a reference oscillator operable to calibrate said low frequency oscillator; a detonation circuit coupled to said microprocessor.
 18. The system of claim 16, wherein the microcontroller further comprises: a power switch electrically coupled to a power supply, said power switch coupled to said microprocessor, said power switch electronically coupled to said reference oscillator, wherein said microprocessor is operable to disconnect power from said reference oscillator.
 19. The system of claim 16, wherein said reference oscillator comprises an enable function operable by said microprocessor.
 20. A method, comprising: receiving ballistic data by a microprocessor from a ballistic computer, wherein said microprocessor is internal to a projectile and said ballistic computer is located external to the projectile in a Fire Control System (FCS); calibrating a low frequency oscillator coupled to said microprocessor via a reference oscillator located in said projectile, wherein said low frequency oscillator is operable to withstand launch accelerations of tens of thousands of g's; powering off said reference oscillator upon completion of said calibrating; and transmitting from said microprocessor a detonation signal to a detonation circuit.
 21. The method according to claim 19, further comprising: enabling said reference oscillator by said microprocessor, wherein said reference oscillator includes an enable function operable by said microprocessor. 